Fails to build on 1.6: type piracy?

[timholy]

Hyperscript doesn't build on nightly. The reason is https://github.com/yurivish/Hyperscript.jl/blob/7731aecafd06e9366020ebee0d6674527fe3d7d6/src/Hyperscript.jl#L117

Here's why: 1.6 has a new TOML parser that includes this line. The issue is that Union{} <: Hyperscript.AbstractNode, because Union{} is a subtype of every other type, and hence instead of creating an array with eltype Union{} it tries (during package loading!) to call Union{}(xs...), which obviously fails. CC @KristofferC.

I am pretty sure this method counts as type-piracy (even if you own YourType, you do not own Vector{YourType}), so I guess the question is, can it be eliminated?

[KristofferC]

I guess it could be written as Vector{Union}() but changing the result of Union{}[] is probably not ideal anyway.

[timholy]

In case someone asks:

julia> using SnoopCompileCore

julia> abstract type AbstractNode{T} end

julia> invs = @snoopr Base.getindex(node::Type{<:AbstractNode}, xs::Any...) = node(xs...);

julia> using SnoopCompile

julia> length(uinvalidated(invs))
358

All the invalidated methods are callers of parse_array. But if you load Revise it goes up to 590.

[timholy]

Hmm, tests pass just fine with

diff --git a/src/Hyperscript.jl b/src/Hyperscript.jl
index 10ca312..8608159 100644
--- a/src/Hyperscript.jl
+++ b/src/Hyperscript.jl
@@ -114,7 +114,8 @@ function Base.typed_hvcat(node::AbstractNode, rows::Tuple{Vararg{Int64}}, xs::An
 end
 Base.typed_hcat(node::AbstractNode, xs::Any...) = node(xs...)
 Base.typed_vcat(node::AbstractNode, xs::Any...) = node(xs...)
-Base.getindex(node::Union{AbstractNode, Type{<:AbstractNode}}, xs::Any...) = node(xs...)
+Base.getindex(node::AbstractNode, xs::Any...) = node(xs...)
+# Base.getindex(node::Union{AbstractNode, Type{<:AbstractNode}}, xs::Any...) = node(xs...)
 
 function Base.:(==)(x::Node, y::Node)
     context(x)  == context(y)  && tag(x)   == tag(y) &&

[SimonDanisch]

@yurivish does anything speak against tagging a new version with your fix?

[timholy]

Meanwhile I think this can be closed. Thanks @yurivish, sorry I didn't notice the fix when it came in.

[yurivish]

@SimonDanisch Not at all, feel free to tag a new version!